Typical telephones generate an audible ringing tone to indicate an incoming call. Some telephones allow the recipient to tailor the ringing tone to a given caller and thereby enable the recipient to become aware of both the incoming call and the identity of the caller when hearing the ringing tone.
Similarly, many computer systems used for the exchange of digital communications (e.g., instant messages or e-mails) allow a recipient to select that a message sound be played upon receipt of a digital communication. The message sound may be played every time a digital communication is received, irrespective of the identity of the sender.
Both the ringing tone and the message sound provide the benefit of informing the recipient of the incoming call or received digital communication without requiring the recipient to look at a screen or a display.